1. Field of the Invention
The present invention relates to a distributor drive system mounted at the front of an engine and configured to eliminate timing fluction problems associated with a distributor mounted at the engine rear.
2. Description of the Prior Art
In certain automobile engines, the distributor is mounted near the rear of the engine housing and is driven from the rear of the cam shaft. The timing gear is mounted at the front of the engine housing and driven from the front of the can shaft. For optimum engine efficiency, the distributor must be synchronized with the timing gear. At low engine RPM the distributor and timing gear generally remain synchronized. However, at higher engine revolution rates three problems occur which cause the distributor to run out of sync with the timing gear. This results in less than optimal power output from the engine.
The first problem concerns the engine oil pump and its associated relief valve. The oil pump shares a common drive with the distributor. When the oil pressure exceeds a certain level, the relief valve opens to bypass the oil back to the pan. The oil pump continues to run, but does not pump oil. As a result, the load on the common distrubutor drive is reduced, causing a shift in the distributor orientation with respect to the cam shaft. Thus, while the engine is running at high speed, each time that the oil pump relief valve opens, the distributor is shifted out of sync with the timing gear. Timing fluctuation occurs, with concomitant loss in engine power.
The second, but related, problem is sometimes referred to as "cam walk". When the relief valve is closed so that the oil pump is pumping, the loading imposed by the operative oil pump actually causes an axial movement of the cam shift toward the front of the engine. A physical movement of 100 thousandths of an inch is typical. This movement shifts the position of the distributor cam sufficiently to vary the ignition timing as much as 10.degree., corresponding to a timing change of as much as 25%.
The third problem is known as "cam flex". In a typical engine the cam shaft is about 2 1/2 feet long. Actual twisting can occur in this cam shaft, with the result that the distributor at the rear of the cam shaft is forced out of sync with the timing gear at the front of the cam shaft. Cam flex is particularly acute in a race car having heavy valve springs. Although the problem occurs at low engine RPM, the effect gets worse as the engine speed increases.
It is an object of the present invention to provide a distributor drive system that will eliminate these timing fluctuation problems.